The present invention relates generally to an apparatus of the type described in my U.S. Pat. No. 4,128,988 for twisting and winding strand material, and more particularly, toward an improvement thereover wherein the strand guide and bobbin are coupled respectively to first and second external electric motors to control the strand tension.
In my U.S. Pat. No. 4,128,988, I describe an apparatus for twisting strand material drawn from an external supply while winding the strand onto a rotating bobbin. The bobbin is mounted on and keyed to rotate with a spindle along a common axis of rotation within an open top pot. The strand is guided onto the bobbin by a hook positioned on the wall of the pot, and during rotation of the pot and bobbin, the pot is axially reciprocated relative to the bobbin to cause layering of strand onto the bobbin body. Strand tension is controlled by controlling a differential between the speeds of rotation of the bobbin and pot in response to the difference between actual strand tension measured by a transducer in the strand supply path and a reference tension.
The spindle, which is journalled in a bolster, is rotated at a constant speed by an external motor coupled to the spindle through a timing belt. The open top pot and strand hook are keyed to the spindle for common rotation. The bobbin, on the other hand, is mounted on a sleeve around the spindle above a flat or "pancake" type electric motor having its stator connected to the pot and rotor coupled to rotate the sleeve and bobbin. Electric current is coupled to the pancake motor by slip rings provided on the outer surface of the pot wall to directly drive the motor and thereby establish the differential speed of rotation between the bobbin and the strand guide on the open top pot as a function of the measured and predetermined reference tensions.
While the provision of a pancake motor within the open top pot for directly establishing the rotational speed differential between the bobbin and strand guide is generally satisfactory and capable of providing excellent performance, it is in some applications preferable to rotate the bobbin and guide using larger external electric motors rather than an internal pancake motor, as in my patent. I have found that external drive motors will increase the versatility of the apparatus since an external drive configuration enables "off-the-shelf" motors having virtually any operating characteristics to be applied. Furthermore, the use of an external drive enables the configuration of the motor to be independent of the configuration of the pot whereby heavy duty applications, such as twisting tire cord, are possible.